HELP UPGRADING COMPUTER FAST

I got myself a nice asus cm6730 PC last year , and I kinda like it very mucha and I wouldn't want to change it , but the gt 530 inside doesn't help me very much with Battlefield 3 , it only gives me like 30 fps on low settings . These are my specs:

So my project is to buy a new graphics card( and a psu for it).These are my choices:

Nvidia gtx 580

Gtx 670

Asus geforce directCU II top gtx 680( more like an dream )

Here we come to the problem. My mobo doesn't really have the pci-e slots required for the gtx670
or the asus gtx 680.
So the question is , What motherboard should I buy ? ( sorry if I got something wrong i'm kinda new in PC upgrading)

The gtx 670 uses a pci-e 3.0 and two 6 pins
The asus gtx680 uses a pci-e 3.0 and a 6pin and 8pin

You most certainly do have a PCI-E slot though it is unlikely to be 3.0 but a 670/680 will work fine as they are backwards compatible. You will probably need to upgrade your PSU to 650W and modern ones have the connections you need.